Question: In physics class, the girl to boy ratio is $6$ to $7$. If there are $12$ girls, how many boys are there?
A ratio of $6$ girls to $7$ boys means that there is a group of $6$ girls for every group of $7$ boys. If there are $12$ girls, then there are $2$ groups of $6$ girls each. Because we know the ratio is $6:7$ , there must be $2$ groups of $7$ boys each. There is a total of $14$ boys in physics class.